Tail Rotor failure in flight

If the tail rotor fails in flight, engine torque can no longer be
countered by the tail rotor, and uncontrolled spinning of the aircraft is
a possibility. Most manufacturers call for an immediate autorotation. Some
call for a running landing, instead. At higher speeds, most aircraft have
enough weathercock stability so that limited amounts of power can be used
to stretch the glide or even to maintain altitude until a suitable landing
area is reached.

Autorotating

An autorotation is a natural way to deal with an inflight tail rotor failure
since it reduces torque to zero. One problem with an autorotation is that it
will be difficult or impossible for the pilot to align the landing gear with
ground track during touchdown. If the helicopter touches down with forward
speed, this could cause a rollover. In calm wind, it is often very difficult
to not have some slide.

One possible solution is for the pilot to use the throttle to help align
the landing gear. Normally transmission drag will yaw the nose slightly
to the left, and engine torque can be used to yaw the nose to the right
until it is lined up with ground track. The major problem is that throttle
manipulation is tricky, and very slow in a turbine aircraft. Meanwhile, the
touchdown phase happens very quickly, giving the pilot little time to
use the throttle.

Running Landing

A running landing can be used to land the helicopter at very low power
settings. If the approach can be set up with a left crosswind, that will
allow even more power to be used without inducing a right yaw. The throttle
can be used to align the skids, and because everything is happening very
slowly, the pilot has more time to react with the throttle.

One negative to this sort of a landing is that pilots tend to practice
autorotations more often than running landings. Touchdown speed in a running
landing with no tail rotor is on the order of 10-20 knots. If the pilot makes
an error and the helicopter is rolled over, people can easilly get hurt at
such high speeds. Autorotations on the other hand tend to terminate at just
a few knots, even on a calm wind day. Mistakes which cause a rollover are
less likely to cause injury because the speeds are probably lower.

Another way to do the running landing

If a shallow approach is possible, another way to land the helicopter is
to make an approach similar to a running landing, but with slightly higher
airspeed. When the skids are quite close to the ground, the pilot flares
to kill ground speed. As airspeed drops off and the helicopter starts to
settle, the pilot uses power to hold the aircraft off the ground, meanwhile
he continues to use cyclic to stop all ground speed. The power will instantly
start torquing the aircraft to the right, but if the pilot continues to use
cyclic to stop ground speed, throttle may be chopped just as ground speed
comes to zero. A normal hovering autorotation is then used to land the
helicopter. As soon as the throttle is chopped, most rotation will stop,
and since the ground speed is zero what little rotation is left is unlikely
to roll the aircraft over. This is my preferred method, and normally I get
about 90 degrees of rotation before I am able to roll off throttle. The
rotation is normally stopped well before touchdown, and I usually induce
a little motion in the direction the skids are pointed with the cyclic,
in order to get a really soft touchdown. Don't use this technique unless
you can get someone to show you how, but if you can find an experienced
pilot to show it to you, I think you'll agree with me this is the best
way to land sans tail rotor. (that doesn't mean ignore the manufacturer,
though).
Paul Cantrellpaul at copters.com
(replace " at " with "@" to email me - this avoids SPAMMERS I hope)